Anxiety disorders are among the most common childhood and adolescent psychiatric disorders and are often associated with academic, social, and family morbidity. These disorders frequently increase the risk for developing other psychiatric disorders (e.g., depression, substance abuse), aggregate in families, and they appear to continue into adulthood. Except for obsessive compulsive disorder, there are very few pharmacological treatment studies for childhood anxiety disorders. Given the sparsity and methodological problems of previous anxiety pharmacological studies, it is clear that further investigation of the use of pharmacological treatment of children and adolescents with these disorders is needed. We propose examining whether or not fluoxetine is an effective and safe treatment for children and adolescents with GAD. In a period of 4 years, 100 children and adolescents ages 8 to 17 years old will participate in a 12 week randomized, double-blind study comparing fluoxetine (fixed dose 20 mg/day) with placebo. Patients will be assessed for psychiatric symptomatology, functional status, and side effects. In addition, to assess attainment of steady state and compliance with treatment, plasma levels of fluoxetine and norfluoxetine will be measured at 4, 8 and 12 weeks. Patients with current major depression or substance abuse, as well as patients with panic and obsessive compulsive disorder will be excluded. To standardize the treatment protocol and to assure that both groups (fluoxetine and placebo) receive equivalent nonpharmacological treatment, a manual will be used. It is hypothesized that patients taking fluoxetine will show significantly more improvement in anxiety symptomatology and functional status than the patients taking placebo without developing significant side effects. Potential predictors of clinical response such as age sex, duration and severity of anxiety, school absenteeism, sub-syndromal depressive symptoms, family history of anxiety or mood disorders will be explored. Our study will be the first step in a series of studies with anxious children and adolescents. Future studies will include the use of other treatment modalities such as cognitive-behavioral therapy and the use of other medications, the development of combined treatments, maintenance treatments, and the evaluation of fluoxetine (and other SSRIs) long term efficacy and side effects.